Thermal voltage control for a christmas tree lighting spring

ABSTRACT

This invention relates to a thermal voltage control for a Christmas tree lighting string which in operation applies two or more slightly varying voltage changes to the lamps of the string thereby to produce a soft twinkling or shimmering of the lamps in pleasing contrast to the on and off effect produced by the conventional flasher.

United States Patent [191 Davis, Jr.

[ THERMAL VOLTAGE CONTROL FOR A CHRISTMAS TREE LIGHTING SPRING [76]Inventor: George Bynum Davis, Jr., 7512 Marbury Rd., Bethesda, Md. 20014[22] Filed: Jan. 17, 1973 [21] Appl. No.: 324,307

[52] US. Cl. 315/72, 315/185 S, 315/186, 315/210, 315/226, 337/16 [51]Int. Cl. H05b 39/02 [58] Field of Search 315/72, 66, 185 R, 185 S,315/186, 225, 226, 309, 210; 337/1, 16, 20,

[56] References Cited UNITED STATES PATENTS 3,047,773 7/1962 Morton315/309 X June 18, 1974 3,143,300 8/1964 Way 315/309 X FOREIGN PATENTSOR APPLICATIONS 596,443 7/1959 Italy 315/210 Primary ExaminerHerman KarlSaalbach Assistant ExaminerJames B. Mullins ABSTRACT 2 Claims, 5 DrawingFigures 1 THERMAL VOLTAGE CONTRGL FOR A CHRISTMAS TREE LIGHTING SPRINGI-Ieretofore numerous mechanisms and arrangements have been devised toproduce an on and off flashing of the lamps of a Christmas tree lightingstring. .The effect produced by such devices is a sudden and drasticchange in lighting intensity that in many instances is distracting andneither pretty nor pleasing. Further, there apparently has been noeffort to control the rate of these flashing intervals which frequentlyare of a duration of less than V2 second. Such spasmodic flashingfurther detracts from the restful and pleasing effect a lightedChristmas tree is supposed to convey.

It is an object of the present invention to produce a thermoresponsivevoltage control for a Christmas tree lighting string that isspecifically designed so as not to flash the lamps connected therewithin a conventional manner as by breaking the circuit thereto or by soreducing the voltage to the lamp filaments as to bring them to a coolingpoint below incandescence, but to slightly and intermittently vary thevoltage to the lamps in predetermined increments and thereby to producein the lamps small changes in lighting intensity and at predeterminedspaced intervals to result in a soft, slow,

and restful shimmering of the lights heretofore unobtainable with anyconventional flasher structure.

While it is understood that the present device may be constructed as anindividual plug in unit for use with any lighting string, it is mostdesirable that it be an integral part of the connector plug or as afixed assembly connected within the lighting string. Since theselighting strings now vary greatly as to the number and voltages of thelamps used therein as well as different wiring arrangements, series orparellel, it is preferable, for maintaining the operationalcharacteristics desired, that the control be designed specifically forand as a fixed component of the lighting string combination with whichit is to be used.

A still further object is to provide a Christmas tree lighting stringwherein the connector plug housing the thermal control for shimmeringthe lamps, further provide for through terminals for connecting to theplug other plug in connectors of other lighting strings in aconventional manner without going through the circuit of the control.

It is a still further object to provide a thermostatic control assemblyof the character disclosed which is so constructed as to enable it beingtested and adjusted prior to assembly within the lighting string,thereby to more positively assure proper operation of the final productwith fewer after assembly rejections.

A further object is to provide for a thermal control as described havingidentical operating parts, thereby reducing the cost of manufacture andfacilitate assembly.

A better understanding of structure and advantage of the device may behad by now referring to the accompanying drawings wherein:

FIG. 1 is an open base view in elevation of the plug in connector of aChristmas tree lighting string showing the arrangement of the thermalcontrol of FIG. 2 arranged therein.

FIG. 2 is a plan view in elevation of the thermal control assemblybefore mounting within the connector plug of FIGS. 1 and 3.

FIG. 3 is a view in elevation of the connector plug as shown in FIG. 1.

FIG. 4 is a schematic circuit diagram of the invention as wired incombination with a series connected Christmas tree lighting string.

FIG. 5 is a simplified variation of the voltage control of FIG. 2 andwherein the resistor element is of carbon or wire prewound beforeassembly and mounted in 0perative relation with the thermoresponsiveelements of the device.

Referring now to the drawings and more particularly to FIG. 1, thedevice of the present invention is shown as including atherrnoresponsive voltage control generally designated 5, and as mountedwithin the connector plug 6 of a series connected lighting string 7 andshown to advantage in FIG. 4.

The control 5 is so constructed as to mount within the connector plugand to the side of the plugs molded center section 8 to which thecontrol is secured as by screws 9 and 10. This center section 8 of theplug is so formed as to rigidly support the extending connector prongs11 and 12 of the plug and beneath which is secured angular springterminal members 13 and 14 which-serve to contact the connector prongsof a similar connector when the latter is plugged into the device in aconventional manner of connecting one such Christmas tree lightingstring with another. It will be here noted that the through circuitthrough the connector, and formed by the connector prongs and angularterminals, does not require that the current to any attaching connectorpass through the mechanism of the voltage control or in any way beaffected thereby.

The voltage control of FIG. 2 is shown as including, preferably, amolded plastic mounting plate 15 so elevated at 16 as to provide amounting flange for the bimetallic strips 17 and 18 secured to theflange as by rivits 19. A terminal wire 20 electrically connects thestrips 17 and 18 together. Over these thermal strips are sleeved tubularfiberglass or asbestos insulating members 21 upon which is wound heatingresistors 22 and 23. Each of these resistors connect respectively to thethermal strip over which it is wound as at 24 with the other end of theresistor extending to wind about and so connect with terminal members 25and 26 respectively as shown. These terminal members are so formed as toinclude angular flange portions 27 and 28 by means of which the controlis secured within the plug connector by screws 9 and 10 as previouslydescribed. Solder tabs extending from members 28 and 11 provide meansfor attaching the terminals of the lighting string 7 as at 29 and 30respectively.

Referring now briefly to the operation of the device thus far described,current, say 115 volts, is applied to the assembly by way of theconnector prongs l1 and 12. By reason that the contact pairs 31 and 32are separated, the heating resistors 22 and 23 are now in series withthe lamps of the string and, as shown in FIG. 4, to

. thereby reduce the voltage to the lamps to its lowest valve namely,say 60 volts. Current now passing through these resistors causing themto heat and in turn apply heat through the insulating members 21 to thestrips 17 and 18 which, as heated, now begin flexing toward contactclosing position. By having slightly different watt heaters or byinitially separating one pair of contacts, say 31, more than contacts 32or by the addition of slightly more insulation 21 between one of thestrips and its heater, one pair of contacts, say 31, will close beforecontacts 32. This closing of contacts 31 shorts out the resistor 22 toincrease the voltage to the lamps by the valve reduced by the resistorto cause a noticeable brightening of the lamps. As the second pair ofcontacts 33 close, the second resistor 23 is shorted voltage to thelamps reduced to a valve to cause the filaments of the lamps to cool toa state below incandescence to result in a flashing effect. Preferably,when only one resistor element is used in the circuit, a 30 volt drop tothe series is sufficient. When two or more resistors are used, the totalvoltage drop, desirably, should not exceed 60 volts. A 20 to 25 voltdrop for each resistor gives a very satisfactory result, particularlywhen three or more strings are in simultaneous operation upon a tree. V

The device of FIG. is'a simplified, easy to construct, variation of thedevice of FIG. 2 and whereinthe resistor 40 is in the form of a carbonrod or a continuous winding of the resistor element 40 upon an insulatedwire core or a core of asbestos or fiberglass rod 41. Over the resistor40 is sleeved, preferably, ceramic tubular beads 42 and 43. Thebimetallic strips 44 and 45 are secured as by spot welding at 46 to theterminal plate 47 with the strips being so formed as to partially wraparound the beads as shown to be cemented thereto as at 58. This cementprovides for securing the beads against movement along the resistor 40as well as to assure a good thermal contact between the beads andstrips. The cement may be of any type suitable, preferably some form offurnace cement. The strips 44 and 45, as mounted upon the terminalmember 47, are secured with the latter to the mounting plate 51 as byrivets 52. Electrical contact is made with the resistor 40 at points 48,49, and 50 with the thermal strip 44 operative to short out itsrespective sections of the resistor between points 48 and 49 and withstrip 45 operative to short out the resistor section between points 49and 50. Thermal conductivity of the terminal member 47 between connectedstrips 44 and 45 is reduced by the cut-out section 53. Mounting andoperation of the device of FIG. 5 is substantially as described for FIG.2, the difference being primarily in the simplicity of construction.

While the devices shown include two resistors and respectivethermo-responsive elements to give three distinct lighting intensityeffects, it is understood that one or three or more such assemblies canbe used as described without varying from the lamp shimmering concept asprovided by the present device. The assembly may be encapsulate within aglass envelope providing the resistance of the heater is greater thanthat of any one of the lamps of the string and is such as to produce thevoltage dropping effect desired and at the dampered operating ratedesired. 1

What I therefore claim and desire to cover by letters patent is:

l. A Christmas tree lighting string including in combination a pluralityof series connected Christmas tree lamps, a connector plug electricallyconnected to the terminals of said series for electrically connectingsaid lighting series to a voltage supply source, a plurality of heatingresistors mounted within said plug and connected in series with thelamps of said string the total resistance value of said resistors notreducing the voltage to the lamps of said series by greater than of thevoltage of said source, a bemetallic thermal respon- .sive striprespectively associated with each resistor and v movable when heated bythe latter to respectively short out its associate resistor to produceabrightening of the lamps of the series proportional to the voltagereducing value of the resistor shorted, a thermal conductive massinterposed between said bimetallic strip and its associate resistor toeffect thermal lag in the heating and cooling of said strip sufficientto reduce to a predetermined retarded frequency, the resistor shortingand non-shorting operating intervals of said strip.

2. A Christmas tree lighting string including in combination a pluralityof series connected Christmas tree lamps, a connector plug electricallyconnected to the terminals of said series for electrically connectingsaid lighting series to a voltage supply source, a plurality of heatingresistors mounted within said plug and connected in series with thelamps of said string with the total resistance valve of said resistorsnot reducing the voltage from said source to said series by greater than80 percent, a bimetallic thermal responsive strip respectivelyassociated with each resistor and movable when heated by the latter torespectively short out its associate resistor to produce a brighteningof the lamps of the series proportional to-the voltage reducing value ofthe resistor shorted, predetermined volumes of thermal conducting massrespectively interposed in heat communicating relation between each saidbimetallic strip and its associate heating resistor to respectivelyretard, in predetermined differing timed sequence, the thermal responseof said strips into and out of their resistor shorting and non-shortingpositions.

1. A Christmas tree lighting string including in combination a pluralityof series connected Christmas tree lamps, a connector plug electricallyconnected to the terminals of said series for electrically connectingsaid lighting series to a voltage supply source, a plurality of heatingresistors mounted within said plug and connected in series with thelamps of said string the total resistance value of said resistors notreducing the voltage to the lamps of said series by greater than 80% ofthe voltage of said source, a bemetallic thermal responsive striprespectively associated with each resistor and movable when heated bythe latter to respectively short out its associate resistor to produce abrightening of the lamps of the series proportional to the voltagereducing value of the resistor shorted, a thermal conductive massinterposed between said bimetallic strip and its associate resistor toeffect thermal lag in the heating and cooling of said strip sufficientto reduce to a predetermined retarded frequency, the rEsistor shortingand non-shorting operating intervals of said strip.
 2. A Christmas treelighting string including in combination a plurality of series connectedChristmas tree lamps, a connector plug electrically connected to theterminals of said series for electrically connecting said lightingseries to a voltage supply source, a plurality of heating resistorsmounted within said plug and connected in series with the lamps of saidstring with the total resistance valve of said resistors not reducingthe voltage from said source to said series by greater than 80 percent,a bimetallic thermal responsive strip respectively associated with eachresistor and movable when heated by the latter to respectively short outits associate resistor to produce a brightening of the lamps of theseries proportional to the voltage reducing value of the resistorshorted, predetermined volumes of thermal conducting mass respectivelyinterposed in heat communicating relation between each said bimetallicstrip and its associate heating resistor to respectively retard, inpredetermined differing timed sequence, the thermal response of saidstrips into and out of their resistor shorting and non-shortingpositions.